Optical proximity sensors, such as the AVAGO TECHNOLOGIES™ HSDL-9100 surface-mount proximity sensor, the AVAGO TECHNOLOGIES™ APDS-9101 integrated reflective sensor, the AVAGO TECHNOLOGIES™ APDS-9120 integrated optical proximity sensor, and the AVAGO TECHNOLOGIES™ APDS-9800 integrated ambient light and proximity sensor, are known in the art. Such sensors typically comprise an integrated high efficiency infrared emitter or light source and a corresponding photodiode or light detector, and are employed in a large number of hand-held electronic devices such as mobile phones, Personal Data Assistants (“PDAs”), laptop and portable computers, portable and handheld devices, amusement and vending machines, industrial automation machinery and equipment, contactless switches, sanitary automation machinery and equipment, and the like.
Referring to FIG. 1, there is shown a prior art optical proximity sensor 10 comprising infrared light emitter 16, light emitter driving circuit 51, light detector or photodiode 12, light detector sensing circuit 53, metal housing or shield 18 with apertures 55 and 57, and object to be sensed 60. Light rays 15 emitted by emitter 16 and reflected as light rays 19 from object 60 (which is in relatively close proximity to optical proximity sensor 10) are detected by photodiode 12 and thereby provide an indication that object 60 is close or near to sensor 10.
As further shown in FIG. 1, optical proximity sensor 10 further comprises metal housing or shield 18 formed of metal and comprising apertures 55 and 57 located over light emitter 16 and light detector 12, respectively, such that at least a first portion of light 15 emitted by light detector 12 passes through aperture 55, and at least a second portion of the first portion 19 of light reflected from object 50 in proximity to sensor 10 passes through aperture 57 for detection by light detector 12. As shown, metal housing or shield 18 may further comprise first and second modules 61 and 63 within which light emitter 16 and light detector 12 are disposed, respectively. The first and second modules 61 and 63 comprise adjoining optically opaque metal inner sidewalls 25 to provide optical isolation between first and second modules 61 and 63.
Many optical proximity sensors generally include a metal shield, such as shield or housing 18 of the type shown in FIG. 1, to provide optical isolation between light emitter 16 and light detector or photodiode 12 so that undesired optical cross-talk between emitter 16 and detector 12 is minimized. See, for example, the Data Sheets corresponding to the AVAGO TECHNOLOGIES™ APDS-9120 Integrated Optical Sensors Preliminary Datasheet and the AVAGO TECHNOLOGIES™ APDS-9800 Integrated Ambient Light and Proximity Sensors Preliminary Datasheet, each of which is hereby incorporated by reference herein, each in its respective entirety.
The amount of reflected, diffracted or refracted IR radiation and undesired crosstalk or interference between light emitter 16 and light detector 12 may also be exacerbated by the presence of a window disposed above sensor 10, which in some applications is provided as part of a portable or other type of electronic device in which proximity sensor 10 is housed and mounted.
FIG. 2 shows a prior art optical proximity sensor 10 with metal shield or housing 18. The optical proximity sensor shown in FIG. 2 is an AVAGO TECHNOLOGIES™ APDS-9120 Integrated Optical Proximity Sensor, which contains a molded plastic substrate 11 upon which are mounted LED 16 and light detector or photodiode 12. Single-piece metal shield 18 covers LED 16 and light detector or photodiode 12 and contains a downwardly projecting light barrier 65 disposed therebetween (not shown in FIG. 2). Electrical contacts 17 provide a means to establish electrical connections between proximity sensor 10 and external devices. In the APDS-9120 optical proximity sensor, metal shield 18 is formed and thinned using conventional metal stamping techniques, and is affixed to the underlying plastic substrate 11 by gluing. The APDS-9120 sensor has an areal footprint of only 4 mm by 4 mm, and thus is quite small.
FIG. 3 shows a prior art optical proximity sensor 10 with a more complicated metal shield or housing 18 than that of FIG. 2. The optical proximity sensor shown in FIG. 3 is an AVAGO TECHNOLOGIES™ APDS-9800 Integrated Ambient Light and Proximity Sensor, which contains a printed circuit board (“PCB”) substrate 11 upon which are mounted LED 16, light detector or photodiode 12, and ambient light sensor 14. The one-piece metal shield 18 covers LED 16, light detector or photodiode 12, and ambient light sensor 14 and contains a downwardly projecting light barrier 65 disposed therebetween. In the APDS-9800 optical proximity sensor, metal shield 18, being of a considerably more complicated shape and geometry than that of FIG. 2, is formed and thinned using more advanced progressive metal stamping techniques, and must be hand-fitted and attached to the underlying PCB by gluing to ensure proper alignment and fit.
As will now be seen, at least some optical proximity sensors of the prior art rely upon the use of an externally mounted metal shield 18, which is required to reduce the amount of crosstalk or interference that might otherwise occur between LED 16 and light detector 12, as well as to help increase the detection distance of the device. Metal shields 18 are quite small, however, making them difficult to manufacture in high volumes, and thus expensive to fabricate. Such metal shields 18 also generally require expensive automated equipment to attach same to sensors 10 in a mass production setting. Moreover, the quality of metal shields 18 often varies, and issues commonly arise with suppliers being unable to meet the tight dimensional tolerances required for such small devices. Metal shields 18 can also detach from sensor 10, thereby adding another failure point for sensor 10.
What is need is an optical proximity sensor design that eliminates the need to include a metal shield 18, but which retains high crosstalk and interference rejection characteristics so that an optical proximity sensor can be provided that features improved performance, lower cost, increased manufacturability and improved reliability.